How do I terminate "wait" function?

Hello,

I want to terminate or interrupt "wait" function if user presses a cancel button in a gui fig.

Here's a part of my code.

% create a dragable box
rect_h=imrect(gca, position);

while (flag)
    % wait until user decides and confirms the box
    rectPos=wait(rect_h);

    % do the rest jobs
      ...
      ...
end

I use "while(flag)" to run the loop until user presses a cancel button. If the cancel button is pressed, the flag is set to false. But the code still stays at

rectPos=wait(rect_h);

until user double clicks to confirm the rectangle.

Any good way to terminate the wait function and escape the while loop by pressing just one cancel button?

Thank you for your help in advance.